Thanks Robert for the tips,
I have tried using the cable release in many variations... including the ones that you mention. But still without any luck. And in the past, it worked just fine for me. So all I can conclude is that "something" happened recently to change what had previously worked just fine. With the adapter plugged in, it was not only the cable release that did not work properly, but also the shutter release button on the camera body did not work properly. As soon as I removed the adapter, then the shutter release button worked fine. So, I think, then the problem is with the adapter (fingers crossed). Once I get a new adapter (in about a week), I'll be sure to follow up and let you know if that was the issue.